U.S. patent application number 10/276301 was filed with the patent office on 2004-02-05 for object processing apparatus and plasma facility comprising the same.
Invention is credited to Ban, Heitaro, Deguchi, Mikio, Ishikawa, Toshiaki, Itatani, Ryohei, Mebarki, Bencherki, Toda, Toshihiko.
Application Number | 20040020598 10/276301 |
Document ID | / |
Family ID | 26592779 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040020598 |
Kind Code |
A1 |
Itatani, Ryohei ; et
al. |
February 5, 2004 |
Object processing apparatus and plasma facility comprising the
same
Abstract
A processing apparatus for subject of the present invention uses
a high voltage electrode and a ground electrode, and generates
plasma under atmospheric pressure in a reaction passage through
which a to-be-processed subject passes. For example, even
fluorocompound such as PFC including CF.sub.4 can effectively be
decomposed because the fluorocompound is brought into contact with
plasma in a small space for sufficient time, and the apparatus has
a small and simple structure. Therefore, the apparatus can be added
to each process chamber.
Inventors: |
Itatani, Ryohei; (Kyoto,
JP) ; Deguchi, Mikio; (Ehime, JP) ; Mebarki,
Bencherki; (Champs-sur-Marne, FR) ; Toda,
Toshihiko; (Ehime, JP) ; Ban, Heitaro; (Ehime,
JP) ; Ishikawa, Toshiaki; (Kyoto, JP) ;
Itatani, Ryohei; (Kyoto, JP) |
Correspondence
Address: |
ARMSTRONG, KRATZ, QUINTOS, HANSON & BROOKS, LLP
1725 K STREET, NW
SUITE 1000
WASHINGTON
DC
20006
US
|
Family ID: |
26592779 |
Appl. No.: |
10/276301 |
Filed: |
November 22, 2002 |
PCT Filed: |
May 28, 2001 |
PCT NO: |
PCT/JP01/04437 |
Current U.S.
Class: |
156/345.29 |
Current CPC
Class: |
B01D 2257/2066 20130101;
Y02C 20/30 20130101; B01D 53/323 20130101; B01D 2257/2064 20130101;
B01D 2257/40 20130101; H05H 1/46 20130101; B01D 2257/30 20130101;
B01D 53/70 20130101; B01D 2257/2062 20130101; H05H 2245/17
20210501; H05H 1/466 20210501; B01D 2257/204 20130101; B01D
2259/818 20130101 |
Class at
Publication: |
156/345.29 |
International
Class: |
H01L 021/306 |
Foreign Application Data
Date |
Code |
Application Number |
May 29, 2000 |
JP |
2000-157936 |
Apr 19, 2001 |
JP |
2001-120454 |
Claims
1. (Amended) A processing apparatus for subject comprising a thin
and long capillary reaction passage through which a to-be-processed
subject passes, a high voltage electrode disposed on the side of
one end of said reaction passage, and a ground electrode disposed
on the side of the other end of said reaction passage, wherein
water is allowed to flow through at least a portion of an inner
wall of said reaction passage, and plasma is generated in an axial
direction of said reaction passage under atmospheric pressure.
2. (Amended) A processing apparatus for subject according to claim
1, wherein said high voltage electrode is disposed on a flow-in
side of said reaction passage.
3. (Amended) A processing apparatus for subject according to claim
1, wherein a plasma chamber is provided on a flow-out side of said
reaction passage.
4. (Amended) A processing apparatus for subject according to claim
1, wherein a portion of said reaction passage is formed of said
ground electrode.
5. (Amended) A processing apparatus for subject according to claim
1, wherein water is supplied from a flow-in side of said reaction
passage, said water is drained from a flow-out side of said
reaction passage.
6. (Amended) A processing apparatus for subject according to claim
1, wherein a water reservoir is formed in an outer periphery of
said reaction passage, water in said water reservoir is supplied to
said reaction passage.
7. (Amended) A processing apparatus for subject according to claim
1, wherein water in said water reservoir is supplied into said
reaction passage from an end of a flow-in side end of said reaction
passage.
8. (Amended) A processing apparatus for subject, wherein a reaction
passage is formed of an insulating material between said high
voltage electrode and said ground electrode, said high voltage
electrode is disposed on a flow-in side of said reaction passage, a
water reservoir is provided on a flow-out side of said reaction
passage, plasma is generated in an axial direction of said reaction
passage under atmospheric pressure.
9. A processing apparatus for subject according to claim 8, wherein
said water reservoir is disposed on an upper surface of said ground
electrode, a flow-out side end of said reaction passage is disposed
below a water surface in said water reservoir, and a flow-in side
end of said reaction passage is formed with an inclined surface
whose outer periphery side is inclined downward.
10. A processing apparatus for subject according to claim 8,
wherein water or water vapor is supplied to the flow-out side of
said reaction passage, water after it was brought into contact with
plasma is drained.
11. (Amended) A processing apparatus for subject according to claim
8, wherein a waterway is provided around said reaction passage,
water which passes through said waterway and which is heated is
supplied into said reaction passage.
12. (Amended) A processing apparatus for subject in which using a
high voltage electrode and a ground electrode, plasma is generated
under atmospheric pressure in a reaction passage through which a
to-be-processed subject passes, wherein said high voltage electrode
is disposed on the flow-in side of said reaction passage, said
ground electrode is disposed in said reaction passage, water is
allowed to flow downward along an inner wall of said reaction
passage, plasma is generated in an axial direction of said reaction
passage.
13. A processing apparatus for subject according to claim 12,
wherein a water reservoir is provided around said reaction
passage.
14. A processing apparatus for subject according to claim 12,
wherein said ground electrode is provided on said inner wall of
said reaction passage.
15. A processing apparatus for subject according to claim 12,
wherein said ground electrode is provided on a center axis of said
reaction passage.
16. A processing apparatus for subject according to claim 12,
wherein said ground electrode is movably provided in a longitudinal
direction of said reaction passage.
17. A processing apparatus for subject according to claim 12,
wherein said plural ground electrode is provided.
18. A processing apparatus for subject according to claim 12,
wherein said high voltage electrode is provided such that it can
move toward and away from said reaction passage.
19. A processing apparatus for subject according to claim 12,
wherein said high voltage electrode is made of platinum.
20 A processing apparatus for subject according to claim 12,
wherein said water is allowed to flow out from the flow-out side of
said reaction passage.
21. (Amended) A plasma system using a processing apparatus for
subject in which using a high voltage electrode- and a ground
electrode, water is allowed to flow downward along an inner wall of
a reaction passage through which a to-be-processed subject passes,
plasma is generated in an axial direction of said reaction passage
under atmospheric pressure, wherein a high vacuum pump is connected
to an exhaust pipe of a process chamber which carries out plasma
processing, a roughing vacuum pump in which a plurality of pumping
units are connected to each other in series is connected to said
exhaust pipe of said high vacuum pump, said processing apparatus
for subject is connected to said exhaust pipe of said roughing
vacuum pump.
22. A plasma system according to claim 21, wherein said processing
apparatus for subject is inserted between said plurality of pumping
units which constitutes said roughing vacuum pump.
Description
TECHNICAL FIELD
[0001] The present invention relates to a processing apparatus for
subject and a plasma system using the same. It is conceived that
gas exhausted from a process chamber, which carries out plasma
processing, such as mainly gas including halogen element, more
concretely, PFC gas such as CF.sub.4 (chlorofluorocarbon 14) and
C.sub.4F.sub.8 (chlorofluorocarbon 318), and CxHyFz, CxHyClz,
CxFyClz, CwFxClyBrz, SF.sub.6, NF.sub.3, CCl.sub.4 and the like (w,
x, y, z are integers) adversely influences the global environment
such as by global warming, destruction of the ozone layer, etc.
Among them, PFC (perfluorocarbon) is extremely stable and thus, if
this gas is not decomposed and is exhausted into atmosphere, damage
is great.
[0002] The above gas is mainly used for an etching apparatus, but
when an inner wall of a CVD apparatus is cleaned or when an
interior of a PVD apparatus is cleaned, the above-described etching
gas is used.
[0003] It is a main object of the present invention to decompose
the above-described etching gas, but other than this, the invention
is also applied to processing of harmful gas and harmful solid or
liquid material if they can be decomposed. Further, the present
invention is mainly applied to the above-described etching
apparatus, and the CVD apparatus and the PVD apparatus when they
are cleaned, but other than those, the invention is also applied to
various kinds of plasma systems which discharge harmful materials
which can be abated.
BACKGROUND TECHNIQUE
[0004] According to most of conventional processing methods of
exhaust gas, the gas is processed by a chemical method under
atmospheric pressure. Normally, in these processing steps, gas
exhausted from each reaction apparatus is collected and
collectively processed under normal atmospheric pressure. That is,
cleaning of gas and other chemical process are carried out using
water by a scrubber or the like.
[0005] According to such a chemical processing method, however, a
to-be-processed subject processing system becomes greater than a
producing system in scale in some cases, and this is not practical
economically.
[0006] On the other hand, there is also proposed a method for
electrically processing the exhaust gas. For example, Japanese
Patent Publication No.H4-80723 relates to processing of CVD gas. In
this publication, magnetic field is applied to a plasma generation
space, various exhaust gases are decomposed and solidified and
collected.
[0007] According to this electrically processing method, however,
an apparatus for applying the magnetic field is required, and its
structure is not always simple and small. Further, gas to be
decomposed is CVD gas, and this method can not efficiently
decompose PFC gas which is highly required to be rendered harmless
in recent years. Further, since this conventional example is
limited to the electric discharge under a reduced pressure
atmosphere, its apparatus must be disposed between a high-vacuum
pump and a roughing vacuum pump. Furthermore, it is troublesome to
separately collect the solidified gas at much expense in
effort.
[0008] In view of the above circumstances, it is an object of the
present invention to provide a processing apparatus for subject and
a plasma system using the same in which the apparatus has small and
simple structure, the apparatus can be added to a plasma system,
the apparatus is inexpensive and can be operated without taking
many hands, the apparatus does not damage an auxiliary system such
as a pump, and decomposing efficiency of harmful material,
especially PFC gas is high.
DISCLOSURE OF THE INVENTION
[0009] A first aspect of the present invention provides a
processing apparatus for subject wherein using a high voltage
electrode and a ground electrode, plasma is generated under
atmospheric pressure in a reaction passage through which a
to-be-processed subject passes.
[0010] According to this aspect, exhaust gas is decomposed when the
gas passes through plasma generated in the reaction passage. At
that time, since the plasma fills the reaction passage over its
entire cross section, the gas can not pass through the plasma
without being excited and reacting, and the gas components are
decomposed efficiently. Especially fluorocompound such as PFC
including CF.sub.4 is extremely stable and thus, a usual processing
method serves no purpose. According to the method of the present
invention, since the fluorocompound is brought into contact with
the plasma in a small space for sufficient time, the fluorocompound
can effectively be decomposed. A basic structure of the invention
is that the pair of electrodes are provided in the reaction
passage, and the apparatus is operated under atmospheric pressure.
Therefore, the structure of the apparatus can be made small and
simple, and the apparatus can be easily added to each processing
machine.
[0011] According to a second aspect of the invention, in the
processing apparatus for subject of the first aspect, the reaction
passage is formed of the ground electrode, the high voltage
electrode is disposed on a flow-in side of the reaction
passage.
[0012] With this aspect, a thin and long reaction passage becomes a
plasma generating space, and plasma is generated in a longitudinal
direction of the reaction passage. The exhaust gas is influenced by
plasma while passing through a long distance in a narrow cross
section and thus, the decomposition efficiency of the exhaust gas
becomes high.
[0013] According to a third aspect of the invention, in the
processing apparatus for subject of the first aspect, the reaction
passage is formed of the ground electrode, a plasma chamber is
disposed on a flow-out side of the reaction passage, an adsorbent
for adsorbing a decomposition product is put in the plasma
chamber.
[0014] With this aspect, if an adsorbent is charged into the plasma
chamber on the outlet side of the reaction passage, the decomposed
gas components can be collected.
[0015] According to a fourth aspect of the invention, in the
processing apparatus for subject of the first aspect, the reaction
passage is formed of the ground electrode, a plasma chamber is
disposed on a flow-out side of the reaction passage, powder
adsorbent into which wool-like buffering agent is mixed is put in
the plasma chamber.
[0016] With this aspect, if the wool-like buffering agent is used,
it is possible to disperse the powder adsorbent in the plasma
chamber substantially uniformly and thus, the gas can be collected
effectively.
[0017] According to a fifth aspect of the invention, in the
processing apparatus for subject of the first aspect, the
to-be-processed subject is brought into contact with water or water
vapor on a flow-out side of the reaction passage.
[0018] With this aspect, since water or water vapor is supplied in
the vicinity of plasma, a water-soluble reaction product in the
exhaust gas can swiftly be eliminated from vapor phase, and
decomposition can be facilitated.
[0019] According to a sixth aspect of the invention, in the
processing apparatus for subject of the first aspect, the
to-be-processed subject is brought into contact with water or water
vapor in the reaction passage.
[0020] With this aspect, since the plasma generated in the reaction
passage is allowed to contact water or water vapor, the reaction
time of plasma becomes long, and decomposition can further be
facilitated.
[0021] According to a seventh aspect of the invention, in the
processing apparatus for subject of the first aspect, one end of
the reaction passage is an insulating material and the other end
thereof is a ground electrode, the high voltage electrode is
disposed on a side of the insulating material.
[0022] With this aspect, even if the amount of flow of the exhaust
gas is small, it is possible to fully fill the reaction passage
with plasma.
[0023] According to an eighth aspect of the invention, in the
processing apparatus for subject of the first aspect, a reaction
passage is formed of an insulating material between the high
voltage electrode and the ground electrode, the high voltage
electrode is disposed on a flow-in side of the reaction passage, a
water reservoir is provided on a flow-out side of the reaction
passage.
[0024] With this aspect, since water in the water reservoir becomes
a liquid electrode, plasma is generated between the high voltage
electrode and the water surface, and the exhaust gas is decomposed
while passing through this plasma region. Among the decomposed
components, water-soluble component is collected in water and thus,
the water-soluble component can be exhausted together with water
and disposed.
[0025] According to a ninth aspect of the invention, in the
processing apparatus for subject of the eighth aspect, the water
reservoir is disposed on an upper surface of the ground electrode,
a flow-out side end of the reaction passage is disposed below a
water surface in the water reservoir, and a flow-in side end of the
reaction passage is formed with an inclined surface whose outer
periphery side is inclined downward.
[0026] With this aspect, plasma is generated between water in the
water reservoir and the high voltage electrode, and the exhaust gas
is decomposed by the plasma. Water which was evaporated from water
surface below the reaction passage made of insulating material is
returned into the water reservoir through an outside of a
substantially truncated conical insulating material. Therefore, a
waterdrop is not attached to the reaction passage, and disturbance
is prevented from being applied to electric discharge.
[0027] According to a tenth aspect of the invention, in the
processing apparatus for subject of the eighth aspect, water or
water vapor is supplied to the flow-out side of the reaction
passage, water after it was brought into contact with plasma is
discharged.
[0028] With this aspect, since plasma generated in the reaction
passage is allow to approach and water or water vapor is supplied,
the reaction with water becomes most active, and decomposition of
the exhaust gas can be facilitated.
[0029] According to an eleventh aspect of the invention, in the
processing apparatus for subject of the first aspect, a waterway is
provided around the reaction passage, water which passes through
the waterway and which is heated is supplied into the reaction
passage.
[0030] With this aspect, since hot water or water vapor which was
heated while passing through the waterway can be supplied into the
reaction passage, reaction between plasma and water is effectively
carried out, and decomposition is facilitated.
[0031] A twelfth aspect of the invention provides a processing
apparatus for subject in which using a high voltage electrode and a
ground electrode, plasma is generated under atmospheric pressure in
a reaction passage through which a to-be-processed subject passes,
wherein the high voltage electrode is disposed on the flow-in side
of the reaction passage, the ground electrode is disposed in the
reaction passage, water is allowed to flow downward along an inner
wall of the reaction passage.
[0032] With this aspect, since the ground electrode is provided in
the gas passage, plasma can be formed a long the reaction passage,
and the reaction passage can be fully filled with plasma over the
entire cross section. Therefore, the contact area with harmful
material which passes through the reaction passage becomes large,
the harmful material and plasma can be reacted reliably and thus,
decomposition of the harmful material can be carried out
efficiently. Especially fluorocompound such as PFC including
CF.sub.4 is extremely stable and thus, a usual processing method
serves no purpose. According to the method of the present
invention, since the fluorocompound is brought into contact with
the plasma in a small space for sufficient time, the fluorocompound
can effectively be decomposed. A basic structure of the invention
is that the pair of electrodes is provided in the reaction passage,
and the apparatus is used under atmospheric pressure. Therefore,
the structure of the apparatus can be made small and simple, and
the apparatus can be added to each process chamber. Further, since
a water layer is formed over the entire surface of the inner wall
of the reaction passage, plasma and water are brought into contact
with each other over a wide area. Therefore, water vapor which was
generated by contact between plasma and water can efficiently be
entangled into plasma. Thus, the decomposition of the harmful
material is facilitated, and water-soluble rection product can be
absorbed by water efficiently. Therefore, decomposition and
separation efficiency of the harmful material can be enhanced.
[0033] According to a thirteenth aspect of the invention, in the
processing apparatus for subject of the twelfth aspect, a water
reservoir is provided around the reaction passage.
[0034] With this aspect, since it is possible to prevent a
temperature of a wall surface of the reaction passage from
excessively rising, it is possible to prevent all of water flowing
down through the reaction passage inner wall from being evaporated.
Therefore, since the reaction passage inner wall is always covered
with the water layer, it is possible to prevent erosion of the
reaction passage inner wall which may be caused by reactive
species.
[0035] According to a fourteenth aspect of the invention, in the
processing apparatus for subject of the twelfth aspect, the ground
electrode is provided on the inner wall of the reaction
passage.
[0036] With this aspect, since the ground electrode is provided
along the inner surface of the reaction passage, water flows along
the inner surface of the ground electrode. Therefore, the ground
electrode is automatically cooled, and it is possible to suppress
the erosion of the electrode. Further, since a harmful material
passes through inside the water layer formed on the inner surface
of the ground electrode, the ground electrode does not act as a
resistance when the harmful material flows through the reaction
passage.
[0037] According to a fifteenth aspect of the invention, in the
processing apparatus for subject of the twelfth aspect, the ground
electrode is provided on a center axis of the reaction passage.
[0038] With this aspect, since the ground electrode comes into
contact directly with plasma, power loss caused by water resistance
can be eliminated.
[0039] According to a sixteenth aspect of the invention, in the
processing apparatus for subject of the twelfth aspect, the ground
electrode is movably provided in a longitudinal direction of the
reaction passage.
[0040] With this aspect, if the ground electrode is brought closer
to the high voltage electrode when electrical discharge is started,
plasma can be formed easily. Further, if the ground electrode is
moved away from the high voltage electrode after the plasma is
formed, a length of the plasma is increased, a space where the
plasma and a harmful material are reacted can be increased and
thus, decomposition and separation efficiency of the harmful
material can be enhanced.
[0041] According to a seventeenth aspect of the invention, in the
processing apparatus for subject of the twelfth aspect, the plural
ground electrodes are provided.
[0042] With this aspect, if the ground electrode which is close to
the high voltage electrode is energized when electrical discharge
is started, plasma can be formed easily. After plasma is formed, if
a ground electrode to be energized is changed to a ground electrode
which is away from the high voltage electrode in sequence, a length
of the plasma can be increased. Therefore, since the space where
the plasma and a harmful material are reacted can be increased,
decomposition and separation efficiency of the harmful material can
be enhanced. Further, since the length of plasma can be changed
only by changing an electrode to be energized, a structure of the
apparatus can be simplified.
[0043] According to an eighteenth aspect of the invention, in the
processing apparatus for subject of the twelfth aspect, the high
voltage electrode is provided such that it can move toward and away
from the reaction passage.
[0044] With this aspect, if the high voltage electrode is moved
toward the reaction passage when electrical discharge is started,
plasma can be formed easily. After plasma is formed, if the high
voltage electrode is moved away from the reaction passage, a length
of the plasma can be increased. Therefore, since the space where
the plasma and a harmful material are reacted can be increased,
decomposition and separation efficiency of the harmful material can
be enhanced. When the harmful material is gas, an amount of
reaction between plasma and a harmful material whose flowing speed
is slow before the harmful material enteres the reaction passage
can be increased. Thus, the decomposition efficiency of the harmful
material can be enhanced.
[0045] According to a nineteenth aspect of the invention, in the
processing apparatus for subject of the twelfth aspect, the high
voltage electrode is made of platinum.
[0046] With this aspect, it is possible to keep a surface of the
high voltage electrode chemically stable, and it is possible to
prevent erosion of the electrode which may be caused by the harmful
material.
[0047] According to a twentieth aspect of the invention, in the
processing apparatus for subject of the twelfth aspect, the water
is allowed to flow out from the flow-out side of the reaction
passage.
[0048] With this aspect, a water-soluble reaction product
discharged from the flow-out side of the reaction passage can
efficiently be absorbed by water and removed, and it is possible to
prevent the exhaust side of the apparatus from being damaged by
heat.
[0049] A twenty-first aspect of the invention provides a plasma
system using a processing apparatus for subject in which using a
high voltage electrode and a ground electrode, plasma is generated
under atmospheric pressure in a reaction passage through which a
to-be-processed subject passes, wherein a high vacuum pump is
connected to an exhaust pipe of a process chamber which carries out
plasma processing, a roughing vacuum pump in which a plurality of
pumping units are connected to each other in series is connected to
the exhaust pipe of the high vacuum pump, the processing apparatus
for subject is connected to the exhaust pipe of the roughing vacuum
pump.
[0050] With this aspect, the exhaust gas in the process chamber is
evacuated by the highvacuum pump and the roughing vacuum pump, and
is decomposed under atmospheric pressure just before the exhaust
gas is exhausted into atmosphere. Therefore, the processing
apparatus for subject can be reduced in size. Further, the exhaust
gas is processed on the flow-out side of the roughing vacuum pump,
hazardous byproduct does not reversely flow toward the process
chamber, and the plasma system is not damaged or its lifetime is
not shortened. The electrical discharge under atmospheric pressure
can shorten a distance between electrodes according to the
similarity law as compared with a case under low vacuum, and as a
result, the apparatus can be reduced in size. Therefore, it is easy
to add the apparatus to each processing machine.
[0051] According to a twenty-second aspect of the invention, in the
plasma system of the twenty-first aspect, the processing apparatus
for subject is inserted between the plurality of pumping units
which constitutes the roughing vacuum pump.
[0052] With this aspect, gas which was not decomposed by a first
processing apparatus for subject provided in the roughing vacuum
pump can be decomposed by a second processing apparatus on the
flow-out side of the roughing vacuum pump. Therefore, it is
possible to further enhance the decomposing efficiency of exhaust
gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 is a block diagram of a plasma system according to an
embodiment of the present invention.
[0054] FIG. 2 is a block diagram of a plasma system of another
embodiment of the invention.
[0055] FIG. 3 is a vertical sectional view showing an embodiment of
a processing apparatus for subject A of the invention.
[0056] FIG. 4 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0057] FIG. 5 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0058] FIG. 6 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0059] FIG. 7 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0060] FIG. 8 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0061] FIG. 9 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0062] FIG. 10 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0063] FIG. 11 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0064] FIG. 12 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0065] FIG. 13 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0066] FIG. 14 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0067] FIG. 15 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0068] FIG. 16 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0069] FIG. 17 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0070] FIG. 18 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0071] FIG. 19 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0072] FIG. 20 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0073] FIG. 21 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0074] FIG. 22 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0075] FIG. 23 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0076] FIG. 24 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0077] FIG. 25 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0078] FIG. 26 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0079] FIG. 27 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
[0080] FIG. 28 is a sectional view of an essential portion showing
another embodiment of the processing apparatus for subject A.
BEST MODE FOR CARRYING OUT THE INVENTION
[0081] Next, embodiments of the present invention will be explained
based on the drawings.
[0082] First, an entire structure of a plasma system to which a
processing apparatus for subject of the invention is applied will
be explained.
[0083] FIG. 1 is a block diagram of the plasma system according to
an embodiment of the invention.
[0084] In FIG. 1, a process chamber 1 carries out plasma
processing. The process chamber in this invention mainly means a
process chamber of an etching apparatus, but also includes a
process chamber for a PVD and a CVD apparatus when apparatus is
cleaned using etching gas, and also includes all process chambers
which discharge a harmful material which can be decomposed by a
later-described processing apparatus for subject A of the present
invention.
[0085] A high vacuum pump 2 and a roughing vacuum pump unit 3 are
connected to an exhaust pipe of the process chamber 1 in this
order. The high vacuum pump 2 is comprised with a known turbo
molecular pump (TMP). The roughing vacuum pump unit 3 comprises
known Roots pumps 4 and 5 which are connected to each other in
series. To evacuate the process chamber 1, the process chamber 1 is
evacuated by the roughing vacuum pump unit 3 to some degree and
then, the process chamber 1 is further evacuated by the high vacuum
pump 2 to such low vacuum that is required for processing. During
processing, gas in the process chamber 1 is exhausted into
atmosphere successively. A known plasma system includes all of the
above-described structures. The present invention is characterized
in that a processing apparatus for subject A is connected to an
exhaust pipe 3a on the flow-out side of the roughing vacuum pump
unit 3.
[0086] As shown in FIG. 1, a gas ballast N.sub.2 is injected to an
exhaust pipe 3b between the upstream Roots pump 4 and the
downstream Roots pump 5. A shaft seal N.sub.2 is injected to the
exhaust pipe of the flow-out side of the downstream Roots pump 5.
This gas ballast N.sub.2 is nitrogen (N.sub.2). Although exhaust
gas does not come into contact with oil, the gas ballast N.sub.2 is
injected from an intermediate portion of the pump to dilute the
exhaust gas so as to prevent some particle from being generated and
making the rotor dirty, and to prevent powder from being generated.
The shaft seal N.sub.2 is also nitrogen (N.sub.2), and the shaft
seal N.sub.2 is injected to prevent the exhaust gas from leaking
outside from a portion of the pump through which a rotation shaft
for driving the rotor of the pump passes.
[0087] Details of the processing apparatus for subject A will be
described later. Its basic structure comprises a reaction passage
13 through which a harmful material such as exhaust gas exhausted
from the process chamber 1 which carries out the plasma processing,
a high voltage electrode 12 and a ground electrode 11 which
generates plasma under atmospheric pressure over the entire cross
section in the reaction passage 13 (see FIG. 3).
[0088] Therefore, according to the plasma system shown in FIG. 1, a
harmful material exhausted from the roughing vacuum pump unit 3 is
physically and chemically decomposed in a plasma space generated
between the high voltage electrode 12 and the ground electrode 11
in the processing apparatus for subject A, the decomposed harmful
material is exhausted into atmosphere in a gas state and thus, the
decomposed harmful material does not flow reversely toward the
roughing vacuum pump unit 3 and the process chamber 1 again. Thus,
the plasma system has a merit that disturbance is not generated in
the plasma process.
[0089] Further, since the processing apparatus for subject A is
disposed in a portion of atmospheric pressure on the exhaust side,
the processing apparatus for subject A has the following
merits:
[0090] (a) Unlike a case in which the apparatus is disposed between
a high vacuum pump and a roughing vacuum pump, even if the
apparatus is inserted into an exhaust path of the pump, there is no
fear that the process itself is adversely influenced, and it is
possible to simply add the apparatus to an existing process
line.
[0091] (b) Although components such as HF and H.sub.2O, which
adversely influence the pump, are included in by-products of plasma
reaction, such components do not pass through the pump.
[0092] (c) Since the electrical discharge under atmospheric
pressure is used, it is possible to shorten a distance between
electrodes according to the similarity law as compared with a case
under a low vacuum, and this is advantageous in terms of
miniaturization of the apparatus.
[0093] (d) Even if moisture or vapor is used in the processing
apparatus for subject A, such moisture or vapor does not approach
upstream of the roughing vacuum pump unit 3. Therefore, the Roots
pumps 4 and 5 and the like are not damaged.
[0094] Next, a plasma system of another embodiment of the present
invention will be explained based on FIG. 2.
[0095] In FIG. 2, the process chamber 1, the high vacuum pump 2,
the roughing vacuum pump unit 3 and the Roots pumps 4 and 5 which
constitute the roughing vacuum pump unit 3 are substantially the
same as those shown in FIG. 1. In this embodiment, a first
processing apparatus for subject A is provided on the exhaust side
of the roughing vacuum pump unit 3, and an auxiliary second
processing apparatus for subject A is added between the Roots pumps
4 and 5 in the roughing vacuum pump unit 3. FIG. 1 shows a basic
structure of the present invention, and FIG. 2 shows its developed
style.
[0096] However, the second processing apparatus for subject A
disposed in the roughing vacuum pump unit 3 must be an apparatus
which does not use water or vapor. This is because that if water or
vapor is leaked, the pumps and bearings used in the pumps are
damaged.
[0097] In the plasma system shown in FIG. 2, gas is primary
processed by the processing apparatus for subject A in the roughing
vacuum pump unit 3 and then, the gas is secondary processed by the
processing apparatus for subject A on the flow-out side of the
roughing vacuum pump unit 3. Therefore, the exhaust gas can be
decomposed almost completely.
[0098] Various embodiments of the processing apparatus for subject
A used in the above plasma system will be explained based on FIGS.
3 to 28.
[0099] The structure of the entire processing apparatus for subject
A and technical idea which is common to other embodiments will be
explained based on the embodiment shown in FIG. 3, and only
features of each embodiment will be partially explained after FIG.
4. Parts having the same function are designated with the same
symbols, and explanation thereof is omitted.
Embodiment shown in FIG. 3
[0100] A reference number 10 represents a body case. The ground
electrode 11 and the high voltage electrode 12 are held in this
order by the body case 10 from downstream toward upstream in a
flowing direction of exhaust gas. The ground electrode 11 is formed
at its central portion with a pipe, i.e., thin and long reaction
passage 13. The high voltage electrode 12 is disposed on a center
axis of the reaction passage 13 in the vicinity of its flow-in
side. In this embodiment, an end of the high voltage electrode 12
is inserted into the reaction passage 13. A DC high voltage power
supply or AC high frequency power supply 14 is connected to the
high voltage electrode 12 through a matching circuit 15. The
reaction passage 13 is provided with an introducing pipe 13a for
introducing exhaust gas to be processed, and the introducing pipe
13a is connected to the exhaust pipe 3a in the roughing vacuum pump
uint 3. A plasma chamber 18 is mounted to the ground electrode 11
on the opposite side from the body case 10. An outlet port of the
plasma chamber 18 is opened into atmosphere or connected to an
exhaust pipe 3b in the roughing vacuum pump unit 3 through a
connector 19. The exhaust gas enters a circumference of the high
voltage electrode 12 in the body case 10 from the introducing pipe
13a, and passes through the plasma chamber 18 through the reaction
passage 13 and exits from the connector 19. Plasma is generated by
electrical discharge of the high voltage electrode 12 in the thin
and long reaction passage 13 in the ground electrode 11, and when
the exhaust gas passes through the narrow cross section, the
exhaust gas is decomposed by plasma into various gas
components.
[0101] In this embodiment, the ground electrode 11 is made of
metal, and the material of the ground electrode 11 has preferably
high conductivity such as brass or copper, but the material is not
limited to those only if the material has a function to generate
plasma. Preferable examples of the high voltage electrode 12 are a
metal pipe metal rod, a carbon rod, a Pt rod, a Ti--Pd alloy rod
and the like, but the material of the high voltage electrode 12 is
not limited to those only if the material has a function to
generate plasma.
[0102] The plasma chamber 18 can be filled with various adsorbents.
If the plasma chamber 18 is filled with Ca(OH).sub.2, it is
possible to adsorb F(Fluorine) which is generated by decomposing
CF.sub.4 in the exhaust gas. It is preferable that the plasma
chamber 18 is detachable and attachable because it is easy to
handle the plasma chamber 18.
[0103] Cooled and not cooled ground electrode 11 and high voltage
electrode 12 are included in the present invention. If the cooled
ground electrode 11 and high voltage electrode 12 are used, it is
effective for continuous operation because a temperature is
prevented from increasing. A cooling method thereof is not limited
only if the function of processing a to-be-processed subject is not
hindered. For example, a cooling water may be supplied into or
drained from a pipe-like high voltage electrode 12, a pipe may be
mounted around the ground electrode 11 and cooling water may flow
therethrough, an annular waterway may be formed around an outer
periphery of the ground electrode 11 and a water supplying/drainig
pipe 16A may be connected to the waterway, and cooling water may
flow therethrough.
[0104] A protection pipe 17 may be put in the reaction passage 13
formed by the ground electrode 11. The protection pipe 17 will be
described later as ceramic pipes 22 and 24, and a ceramic
insulative pipe is used as the protection pipe 17 for preventing
erosion. As shown in FIG. 3, if one end of the protection pipe 17
is allowed to extend such as to cover a tip end of the high voltage
electrode 12, abnormal discharge is less prone to be generated.
[0105] The processing apparatus for subject A of the present
invention is used in an environment in which plasma is discharged
under substantially atmospheric pressure. It is the object of the
present apparatus to decompose and eliminate harmful gas by plasma.
Therefore, a condition required for the electrical discharge is
that exhaust gas passing through the apparatus reliably passes
through the plasma region, and the exhaust gas does not pass
without stopping without receiving energy of electrical discharge.
For this purpose, it is necessary to satisfy one of the following
conditions:
[0106] (1) Plasma is continuously generated (there is no instant at
which plasma gose out); and
[0107] (2) Even if there is an instant at which plasma goes out, a
staying time of gas molecule in the plasma region (time required
for the gas molecule to pass through the plasma region) is longer
than an instant at which the plasma goes out.
[0108] It is preferable that the power supply 14 and the reaction
passage 13 constituting the plasma region satisfy the following
conditions.
[0109] First, the power supply preferably has DC or high frequency
of about frequency 10 kHz or higher. A reason thereof is as
follows.
[0110] Generally, when a DC electric field is applied between
electrodesunder atmosheric pressure, it is said that voltage of
about 30 kV per a distance of 1 cm is required for generating
electrical discharge. In an actual electrical discharging
apparatus, an electrode certainly has an edge, an electric field at
that portion becomes strong, voltage required for the electrical
discharge becomes lower than the electric field, and the electrical
discharge is generated at about 10 kV when a distance between
electrodes is 1 cm in some cases. This is in the case of DC, but
also in AC of about commercial frequency, the condition is the
same. However, in a region where the frequency exceeds some ten
kHz, voltage required for electrical discharge becomes smaller.
[0111] In summary, DC electrical discharge satisfies the condition
(1). However, secondary problems, that cathode is heated, power
loss caused by stable resistance of electrical discharge is large,
and high voltage DC power supply is required are caused. For this
reason, it is preferable to use AC voltage, but in order to
sufficiently satisfy the condition (2), higher frequency is
advantageous. In any cases, although voltage and frequency for the
electrical discharge are suitably in the above ranges, in reality,
an optimal value maybe obtained by experiment or design based on a
distance between electrodes of an actual apparatus.
[0112] In order to decompose the exhaust gas, it is preferable that
the entire cross section of a path through which gas passes is
filled with plasma. A diameter of plasma generated by electrical
discharge depends upon a magnitude of current, but if the reaction
passage 13 is made thin, plasma is spread over the entire cross
section of the reaction passage 13, and exhaust gas to be processed
passes through the plasma region without fail. At the thinned
portion, a temperature of plasma is increased and thus, the
decomposition of gas molecule to be processed in the plasma is
further facilitated. Therefore, the reaction passage 13 which
generates plasma has a thin and long cross section. However, if the
cross section is thin or long, a resistance of gas flow becomes
great and thus, its numeric value can not be determined sweepingly.
Therefore, its optimal value may be obtained by experiment or
design. A preferable inner diameter of the reaction passage is
about 3 to 5 mm in terms of spreading manner of plasma of
electrical discharge under atmospheric pressure.
[0113] Next, another embodiment of the processing apparatus for
subject A will be explained based on FIGS. 4 to 28. Only structure
peculiar to each embodiment will be explained below.
Embodiment shown in FIG. 4
[0114] In this embodiment, the reaction passage 13 is not provided
with protection pipe, and the reaction passage 13 is constituted by
the ground electrode 11. As shown in this embodiment, an end of the
high voltage electrode 12 may not always be inserted into the
reaction passage 13. A diameter d of the reaction passage 13 is 3
mm, and a length thereof is 20 mm. If such a thin and long plasma
region is provided in this manner, the decomposition of exhaust gas
molecule is further facilitated.
[0115] A reference number 21 represents a sealing material for
preventing gas from leaking between the ground electrode 11 and the
plasma chamber 18 or body case 10.
Embodiment shown in FIG. 5
[0116] In this embodiment, an inner wall of the reaction passage 13
is provided with a protecting ceramic pipe 22. As shown in FIG. 5,
an end of the ceramic pipe 22 on the side of the high voltage
electrode 12 is flushed with an end of the ground electrode 11, and
the other end of the ceramic pipe 22 on the flow-out side projects
from the end of the ground electrode 11. A ceramic material used
for the ceramic pipe 22 is not limited only if erosion of the
ground electrode 11 can be prevented, but alumina and the like are
preferable for preventing the erosion.
[0117] In this embodiment, since the metal ground electrode 11 does
not come into contact directly with plasma, erosion of the ground
electrode 11 can be prevented by reactive species generated when
gas to be processed is decomposed by plasma. Therefore, the ceramic
pipe 22 may be longer than the reaction passage 13 of the ground
electrode 11.
Embodiment shown in FIG. 6
[0118] In this embodiment, a tip end of the high voltage electrode
12 is covered with a ceramic coating 23.
[0119] By covering the tip end in this manner, the tip end of the
high voltage electrode 12 is prevented from being worn, and the
lifetime of the electrode can be elongated.
Embodiment shown in FIG. 7
[0120] In this embodiment, an outer periphery of the high voltage
electrode 12 is provided with a cylindrical ceramic pipe 24, and
protection gas g is allowed to flow between the high voltage
electrode 12 and the ceramic pipe 24. A tip end of the high voltage
electrode 12 is slightly recessed inward from a tip end of the
surrounding ceramic pipe 24. Preferable examples of the protection
gas g are nitrogen, argon, helium and the like.
[0121] According to this embodiment, plasma on the tip end of the
high voltage electrode 12 is generated by ionization of the
protection gas g, and reactive species generated by decomposition
of to-be processed gas G does not reach the tip end of the
electrode 12. Therefore, it is possible to prevent the erosion of
the high voltage electrode 12 and its lifetime can be
elongated.
[0122] Water vapor may be allowed to flow as protection gas g. In
this case, the water vapor can protect the high voltage electrode
12.
Embodiment shown in FIG. 8
[0123] In this embodiment, in any one of the embodiments shown in
FIGS. 4 to 7, a mixture of wool-like buffering agent 25 and powder
adsorbent 26 is disposed in the plasma chamber 18 in the vicinity
of an outlet port of a reaction passage 13.
[0124] Preferable examples of the wool-like buffering agent 25 are
glass wool, steel wool and the like, and preferable examples of the
powder adsorbent 26 are calcium hydroxide and the like.
[0125] In this embodiment, by disposing the sorbent 26 in the
immediately vicinity of plasma injecting from the reaction passage
13, reactive species decomposed and generated by plasma is
efficiently reacted with sorbent 26 before its reactive force is
not weakened, and decomposition can substantially be facilitated.
Therefore, when the gas to be processed is CF.sub.4, if calcium
hydroxide is used as the sorbent 26, F atom generated by
decomposing CF.sub.4 is trapped as CaF.sub.2, the decomposition can
be facilitated.
[0126] In this embodiment, the structure shown in FIG. 8 may
vertically be reversed, the high voltage electrode 12 may be
disposed at a lower portion and the sorbent may be disposed at an
upper portion, and the exhaust gas G may be allowed to flow from
below to above. In this case, since the sorbent 26 is always
located in the vicinity of the injecting port of plasma by gravity,
effect for trapping the reactive species is improved.
Embodiment shown in FIG. 9
[0127] In this embodiment, in any one of the embodiments shown in
FIGS. 4 to 7, water is supplied inward from a periphery of the
reaction passage at an outlet port of the reaction passage 13 of
the ground electrode 11. Therefore, the plasma chamber 18 near the
ground electrode 11 is provided with a supply passage 27 and a
running water guide 28 which introduces water to the outlet port of
the reaction passage 13.
[0128] In this embodiment, by supplying water in the immediately
vicinity of plasma injecting from the reaction passage 13, reactive
species decomposed and generated by plasma can be reacted with
water, water-soluble reaction product can be swiftly discharged out
from vapor phase, and decomposition can be substantially
facilitated. When gas to be processed is CF.sub.4, if the gas is
reacted with water, CF.sub.4 is decomposed to generate F atom, the
F atom dissolves in water and trapped and thus, the decomposition
can be facilitated.
[0129] Further, by continuously flowing water, absorbing effect of
decomposition product can continuously be maintained. Alkaline
material such as sodium hydroxide, potassium hydroxide, ammonia or
the like may dissolve in water. In this case, when CF.sub.4 is
decomposed and F ion dissolves in water, the water becomes strongly
acid in the as-is state, but the water is immediately neutralized,
and there is a merit that erosion of a drain system can be
suppressed.
[0130] A material (such as calcium hydroxide) having high
reactivity with respect to a reactive product may be dissolved in
water. In this case, when CF.sub.4 is decomposed and F ion
dissolves in water, there is a merit that the component can be
precipitated and removed immediately.
[0131] In the embodiment shown in FIG. 9, water vapor may be
introduced to the supply passage 27 and the running water guide
28.
[0132] In this embodiment, since an amount of heat of plasma is not
absorbed by heating and evaporation of water, water and reactive
species generated by decomposing to-be processed gas G are reacted
with each other at vapor phase (in plasma) without lowering a
temperature of plasma.
[0133] The gas is cooled in the downstream portion, the water vapor
is liquefied, and water-soluble decomposition product may be
removed together with water.
Embodiment shown in FIG. 10
[0134] In this embodiment, in any one of the embodiments shown in
FIGS. 4 to 7, water is inwardly injected from a periphery of the
reaction passage 13 at an inlet port of the reaction passage 13 of
the ground electrode 11 or at an intermediate portion of the
reaction passage 13. For this purpose, a water supply passage 29
which passes through the ground electrode 11 for guiding water into
the reaction passage 13 is formed.
[0135] In this embodiment, since an amount of heat of plasma is not
absorbed by heating and evaporation of water, water and reactive
species generated by decomposing to-be processed gas G can be
reacted with each other at vapor phase (in plasma) without lowering
a temperature of plasma, and decomposition can be facilitated. In
this embodiment, as compared with the embodiment shown in FIG. 9,
since a section where water and plasma act on each other is long,
the reaction is further facilitated.
[0136] In this embodiment, although a portion of drained water is
evaporated by heat of plasma, most of water stays in its as-is
state, and is poured along an inner wall of the reaction passage,
and a discharging amount of water may be controlled such that a
surface of the water becomes the ground side electrode. In this
case, since the inner wall of the reaction passage is covered with
always newly supplied water, there is effect that erosion of
reaction passage inner wall by reactive species is prevented.
[0137] In this embodiment, it is preferable that a plurality of
discharge ports 29a of water or water vapor are provided in
intermediate portions of the reaction passage 13 in its
circumferential direction. The plurality of discharge ports 29a of
water or water vapor may be provided in the vertical direction.
With this design, there is effect that mixing of water and plasma
is more facilitated, and reaction between water and to-be processed
gas G is more activated.
[0138] In the embodiment shown in FIG. 10, water vapor may be
introduced into the water supply passage 29.
[0139] In this embodiment, as compared with a case in which water
is introduced, an amount of heat of plasma is not absorbed by
heating and evaporation of water, water and reactive species
generated by decomposing to-be processed gas can be reacted with
each other at vapor phase (in plasma) without lowering a
temperature of plasma. The gas is cooled in the downstream portion,
the water vapor is liquefied, and water-soluble decomposition
product may be removed together with water.
[0140] In this embodiment, it is preferable that a plurality of
discharge ports 29a of water or water vapor are provided in
intermediate portions of the reaction passage 13 in its
circumferential direction. The plurality of discharge ports 29a may
be provided in the vertical direction. With this design, mixing
between water vapor and plasma is further facilitated, there is
effect that the reaction between water and to-be processed gas G is
more activated.
[0141] In this embodiment, a pipe having an outer diameter which is
smaller than an inner diameter of the reaction passage 13 may be
inserted into a side surface of the reaction passage 13, a surface
of a sidewall of this pipe downstream in the flowing direction of
the to-be processed gas may be provided with a discharge port of
water or water vapor. With this design, an initial velocity of
water or water vapor when it is discharged can be directed
substantially in parallel to a flow of the to-be processed gas, and
there is effect that to-be processed gas G flows easily.
Embodiment shown in FIG. 11
[0142] This embodiment is based on the embodiment shown in FIG. 10,
the discharge port 29a formed on a tip end of the water supply
passage 29 for water or water vapor is directed diagonally
downward, an initial velocity component having the same direction
as that of the flow of to-be processed gas G is applied to water or
water vapor, and the water or water vapor is discharged.
[0143] As compared with the embodiment shown in FIG. 10, the
embodiment shown in FIG. 11 has effect that to-be processed gas G
in the reaction passage 13 flows easily.
[0144] When the inner wall of the reaction passage 13 is provided
with a ceramic pipe (see a symbol 22 in FIG. 6), it is preferable
that the ceramic pipe is provided with the above-described
discharge port 29a.
[0145] In this embodiment, it is preferable that a plurality of
discharge ports 29a of water or water vapor are provided in
intermediate portions of the reaction passage 13 in its
circumferential direction. The plurality of discharge ports 29a may
be provided in the vertical direction. With this design, mixing
between water or water vapor and plasma is further facilitated, and
there is effect that the reaction between water and to-be processed
gas G is more activated.
[0146] In this embodiment, a pipe having an outer diameter which is
smaller than an inner diameter of the reaction passage 13 may be
inserted into a side surface of the reaction passage 13, a surface
of a sidewall of this pipe downstream in the flowing direction of
the to-be processed gas may be provided with a discharge port of
water or water vapor. With this design, an initial velocity of
water or water vapor when it is discharged can be directed
substantially in parallel to a flow of the to-be processed gas, and
there is effect that to-be processed gas G flows easily.
Embodiment shown in FIG. 12
[0147] This embodiment is based on the embodiment shown in FIG. 11.
A gap 30 is provided between an upper edge and a lower edge of the
discharge port 29a of the water or water vapor.
[0148] With this design, an initial velocity of water or water
vapor in the same direction as the flowing direction of the to-be
processed gas G when the water or water vapor is discharged can
increased, and there is effect that to-be processed gas G flows
easily.
[0149] In this embodiment, it is preferable that a plurality of
discharge ports 29a of water or water vapor are provided in
intermediate portions of the reaction passage 13 in its
circumferential direction. The plurality of discharge ports 29a may
be provided in the vertical direction. With this design, mixing
between water or water vapor and plasma is further facilitated, and
there is effect that the reaction between water and to-be processed
gas G is more activated.
Embodiment shown in FIG. 13
[0150] In this embodiment, a discharge port of water or water vapor
is formed by gaps of two kinds of pipes having different diameters.
Therefore, a pipe 31 having a small diameter and a pipe 33 having a
large diameter are concentrically disposed around an inner
periphery of the reaction passage 13 of the ground electrode 11, an
upper portion of the gap between both the pipes 31 and 32 is in
communication with the water supply passage 29, and a lower portion
of the gap is a discharge port 29b.
[0151] In this embodiment, an initial velocity of water or water
vapor when it is discharged can be directed substantially in
parallel to a flow of the to-be processed gas G, and there is
effect that to-be processed gas G flows easily.
Embodiment shown in FIG. 14
[0152] In this embodiment, an insulating material 33 is laminated
on an upper surface of the ground electrode 11, and the ground
electrode 11 and the insulating material 33 form a thin and long
reaction passage 13. That is, the insulating material 33 is
provided on an upper portion of the reaction passage 13, and the
ground electrode 11 is disposed on the flow-out side of the
reaction passage 13.
[0153] With this design, even when the amount of flow of the to-be
processed gas G is small, it is possible to fill the reaction
passage 13 with plasma.
Embodiment shown in FIG. 15
[0154] In this embodiment, water is injected from between the
insulating material 33 and the ground electrode 11. Therefore, the
water supply passage 29 is formed between the insulating material
33 and the ground electrode 11.
[0155] This embodiment has the same effect as that of the
embodiment shown in FIG. 14, and the reliability of protection of
the ground electrode 11 by water is enhanced.
Embodiment shown in FIG. 16
[0156] As shown in FIG. 16, the high voltage electrode 12 and the
ground electrode 11 are disposed such as to be opposed to each
other, and the water reservoir 41 and the insulating material 33
are disposed on an upper surface of the ground electrode 11 in this
order. The insulating material 33 is formed at its central portion
with the thin and long reaction passage 13, and the high voltage
electrode 12 is located above the central portion. Water is
supplied into the water reservoir 41, and the ground electrode 11
is disposed on the bottom of the water reservoir 41. An outlet of
the reaction passage 13 projects under a water surface in the water
reservoir 41 so that the to-be processed gas G becomes bubbles and
passes through water. A water supply pipe 42 is connected to the
water reservoir 41, and the water reservoir 41 is provided at its
upper portion with a water level adjusting hole 43. If water is
always supplied from the water supply pipe 42 and is discharged
from the water level adjusting hole 43, it is possible to always
reserve new water while constantly maintaining the water level. An
exhaust port 44 is formed from a lower surface to a side surface of
the insulating material 33 so that processed exhaust gas G can be
exhausted to atmosphere while passing through water.
[0157] In this embodiment, water in the water reservoir 41 is in
communication with the ground electrode 11 and as a result, the
water constitutes a liquid electrode. Therefore, if high voltage or
high frequency voltage is applied to the high voltage electrode 12,
plasma is generated in the reaction passage 13 between the high
voltage electrode 12 and the water surface. While the to-be
processed gas G passes through the plasma region, the gas G is
decomposed and passes through water, and again exits from the water
and is exhausted out from the exhaust hole 44 formed in an upper
portion of the water reservoir 41. Soluble component among the
components decomposed during this time is trapped in water, and
non-soluble component is discharged into atmosphere. Water in the
water reservoir 41 may be or may not be circulated, but if new
water is always supplied and old water is drained, it is possible
to continuously discharge the decomposed gas components together
with water. The processed gas may be exhausted from the water level
adjusting hole 43 together with water.
[0158] In a plasma system to which the present invention is
applied, gas such as PFC and CF.sub.4 is used. The exhaust gas of
CF.sub.4 is diluted with N.sub.2 when it is exhausted, and is
impurified by O.sub.2 generated in an etching step of SiO.sub.2 in
some cases. Therefore, the exhaust gas includes water-soluble NOx
such as NO.sub.2and NO.sub.3. The processing apparatus for subject
A of the present embodiment uses a water electrode. Therefore,
electrical discharge product after decomposition is not exhausted
into atmosphere, and the product can immediately dissolves in
water, and it is possible to flow out the product together with
water.
[0159] Next, decomposition rate of the processing apparatus for
subject A of the present embodiment will be explained. Gas
exhausted from the process chamber is decomposed to F or C by
decomposing effect by plasma. That is, when the gas passes through
the plasma region, CF.sub.4 is decomposed into CF.sub.3, CF.sub.2,
CF, C, an ion thereof and the like. According to an experiment
using the processing apparatus for subject A of the present
embodiment, an amount of F ion included in water after decomposing
processing was analyzed and as a result, since substantially the
same amount as that of F ion included in used CF.sub.4 gas was
detected, it was found that substantially 100% of CF.sub.4 was
decomposed.
Embodiment shown in FIG. 17
[0160] In this embodiment, an inner wall of the reaction passage 13
provided in the insulating material 33 is heated to 100.degree. C.
or higher by a heater 45.
[0161] With this, a temperature of gas in a plasma region of the
reaction passage 13 is increased, chemical reaction in plasma is
facilitated, moisture mixed in the reaction passage 13 by diffusion
of vapor or vibration of water surface attaches to the inner wall
of the reaction passage 13 as a waterdrop, and disturbance can be
prevented from being applied to electric discharge.
Embodiment shown in FIG. 18
[0162] This embodiment is based on the embodiment shown in FIG. 16,
and an inner diameter of the reaction passage 13 upstream from its
exit is increased. That is, only a portion of the reaction passage
13 in the vicinity of its exit has thin and narrowed cross section.
Even with such a shape, the reaction passage 13 is filled with
plasma and thus, exhaust gas can be decomposed.
[0163] According to this embodiment, disturbance applied to
electrical discharge by a waterdrop which is attached to the inner
wall of the reaction passage 13 can be minimized.
Embodiment shown in FIG. 19
[0164] This embodiment is based on the embodiment shown in FIG. 18.
Portions of the insulating material 33 for restricting the reaction
passage 13 except its portion which is in water and a trapping and
exhausting portion of processed gas are removed, and a container
wall of the water reservoir 41 are used as the reaction passage.
Therefore, the insulating material 33 comprises a truncated conical
cylindrical upper end 33a and a cylindrical lower end 33b, and a
center opening of the upper end 33a serves as the reaction passage
13. The insulating material 33 is supported in the water reservoir
41. A water level adjusting pipe 48 is inserted into the water
reservoir 41 such that the pipe 48 stands up therein, and an upper
end of the pipe 48 is located in the upper end 33a of the
insulating material 33. Therefore, the water level in the water
reservoir 41 is maintained such that an outer periphery of the
upper end 33a of the insulating material 33 comes into water. That
is, the flow-out side end of the reaction passage 13 is located in
water. The high voltage electrode 12 is located on the flow-in side
of the reaction passage 13.
[0165] According to this embodiment, water evaporated from the
water surface of the electrical discharge portion can be returned
from outside of the upper end 33a into the water reservoir 41, and
water is not attached to the inner wall of the reaction passage 13.
Therefore, disturbance applied to electrical discharge by a
waterdrop can be minimized.
[0166] If the water level adjusting hole is constituted by the pipe
48 inserted from a bottom of the water reservoir 41 as in this
embodiment, it is possible to freely change a set water level by
length of the inserted pipe 48. This pipe 48 may be replaced by the
water level adjusting hole 43 in the embodiments shown in FIGS. 16
to 18.
Embodiment shown in FIG. 20
[0167] In this embodiment, the thin and long reaction passage 13 is
formed in a center of the insulating material 33 located below the
high voltage electrode 12, an insulative bottomed cylindrical body
46 is disposed in the water reservoir 41 disposed between the
insulating material 33 and the ground electrode 11. A bottom of the
cylindrical body 46 is opened so that water is supplied to the
cylindrical body 46, and a top of the cylindrical body 46 is
provided at its central portion with a fine hole 46a. Water
supplied to the cylindrical body 46 passes through the upper end
fine hole 46a and is drained toward an exit of the reaction passage
13, and the water works as a water electrode. The waterdrops along
an outer surface of the cylindrical body 46, and enters into the
water reservoir 41, and is discharged from a water channel provided
with the ground electrode 11 in its bottom.
[0168] With this embodiment, new water is always supplied to a
portion where the reaction with water is most active and where
plasma and water come into contact with each other, and there is
effect that the reaction is facilitated.
Embodiment shown in FIG. 21
[0169] In this embodiment, a heater 45 is provided in the
insulating material 33, and another heater 45 is also provided in
the water reservoir 41. The ground electrode 11 provided on a
bottom of the water reservoir 41 is provided with a water supply
port, and an exhaust pipe 47 stands up in the water reservoir 41.
An upper end of the exhaust pipe 47 is located in the vicinity of
the flow-out side of the reaction passage 13, and a lower end of
the exhaust pipe 47 passes through the ground electrode 11.
[0170] In this embodiment, water in the water reservoir 41 works as
a ground side electrode of the electrical discharge, the water in
the water reservoir 41 is heated and evaporated by the heater 45,
and is introduced into the electrical discharge space of the
reaction passage 13 from its lower end as the water vapor.
[0171] This embodiment has the same effect as the water vapor in
the embodiments shown in FIGS. 9 and 10, and has the same feature
as that of the embodiment shown in FIG. 18. Further, since the
metal ground electrode 11 does not come into contact with plasma,
there is effect that erosion is not generated in the ground
electrode 11. Further, by heating the water in the water reservoir
41, the entire reaction passage 13 is maintained at a high
temperature, and there is effect that the decomposition is
facilitated.
Embodiment shown in FIG. 22
[0172] In this embodiment, water is heated by heat which is
generated by electrical discharge, and the water is allowed to be
evaporated and introduced into the electrical discharge space as
water vapor. For this purpose, a waterway 61 which extends along a
gas-flowing direction is provided in an inner wall portion of the
insulating material 33 in the vicinity of the reaction passage 13,
the water supply passage 29 is connected to an upper end of the
waterway 61 (closer to the high voltage electrode 12), a water
vapor discharging hole 62 which is opened toward the reaction
passage 13 is formed at a lower end of the waterway 61 (further
from the high voltage electrode 12).
[0173] In this embodiment, since water is heated by plasma in the
reaction passage 13 while the water passes through the waterway 61,
there are merits that the same effect as that of the embodiment
shown in FIG. 21 can be obtained, it is unnecessary to separately
provide a heater for heating the water, and utilizing efficiency of
power is enhanced.
Embodiment shown in FIG. 23
[0174] In this embodiment, the inner wall of the reaction passage
13 comprises a porous ceramic pipe 63, and a waterway 64 is formed
around the porous ceramic pipe 63. The waterway 64 is provided in
the insulating material 33, water is supplied from the supply
passage 29, and a portion of the water comes into contact with the
ground electrode 11.
[0175] According to this embodiment, water is heated while it
passes through the waterway 64, hot water or water vapor penetrates
into an interior of the reaction passage 13 over its entire length
from the porous ceramic pipe 63, and the hot water or water vapor
can be introduced into the electrical discharge space.
[0176] With this design, water uniformly exudes from the entire
surface of the inner wall of the reaction passage 13, reaction
between plasma and water or water vapor is uniformly taken place
over the entire reaction passage, and there is effect that the
reaction is effectively carried out.
Embodiment shown in FIG. 24
[0177] In FIG. 24, the hollow body case 10 is provided at its upper
portion with an introducing pipe 13a which introduces, into the
body case 10, a harmful material such as exhaust gas to be
processed. This introducing pipe 13a is connected to the exhaust
pipe 3a of the roughing vacuum pump unit 3.
[0178] The body case 10 is formed at its lower end with an exhaust
port 10c which brings an interior and an exterior of the body case
10 into communication with each other. The lower end of the body
case 10 is provided with a cooling water passage 81 which supplies
water into the exhaust port 10c.
[0179] In the body case 10, a reaction pipe 13b is perpendicularly
mounted to an upper end of the exhaust port 10c, and an interior of
the reaction pipe 13b serves as the reaction passage 13. If an
inner diameter of the reaction pipe 13b is about 8 to 20 mm, it is
possible to form plasma over the entire cross section of the
reaction passage 13, and the preferable inner diameter thereof is
about 15 mm because a harmful material can be processed
efficiently. Examples of raw materials of the reaction pipe 13b are
insulations such as alumina, aluminum nitride, silicon nitride,
silicon carbide, boron nitride and the like.
[0180] In the reaction pipe 13b, the ground electrode 11 is
provided along an inner surface of the reaction pipe 13b. Examples
of raw materials of the ground electrode 11 are metals having high
conductivity such as brass, copper and the like.
[0181] A preferable material for the ground electrode 11 is a metal
such as gold and platinum having high conductivity and chemical
stability, and the material is not limited to those only if the
material can generate plasma.
[0182] The body case 10 is provided at its upper end with the high
voltage electrode 12 made of platinum. A lower end of the high
voltage electrode 12 is disposed in the vicinity of an upper end of
the reaction pipe 13b. The power supply 14 is connected to an upper
end of the high voltage electrode 12 through the matching circuit
15. This power supply 14 is a DC high voltage power supply or an AC
high frequency power supply.
[0183] If the power supply 14 is the DC high voltage power supply,
the matching circuit 15 is unnecessary.
[0184] Therefore, if voltage is applied from the power supply 14 to
the high voltage electrode 12, electrical discharge is generated
between the high voltage electrode 12 and the ground electrode 11,
and plasma is formed on an interior, i.e., over the entire cross
section of the reaction passage 13 from the reaction pipe 13b.
Therefore, if a harmful material is introduced into the body case
10 from the introducing pipe 13a, the harmful material comes into
contact with the plasma when the harmful material passes through
the reaction pipe 13b, and the harmful material is decomposed into
various gas components and then is exhausted outside.
[0185] Further, since the raw material of the high voltage
electrode 12 is platinum, a surface of the high voltage electrode
12 can be maintained chemically stable. Therefore, it is possible
to prevent the high voltage electrode 12 from being corroded by the
harmful material.
[0186] Further, if water is supplied to the exhaust port 10c from
the cooling water passage 81, water-soluble reaction product
discharged from the reaction passage 13 can efficiently be absorbed
by water and removed, and it is possible to prevent the exhaust
side of the apparatus from being damaged by heat.
[0187] When the electrical discharge is started, if pulse voltage
higher than voltage when the electrical discharge is started is
applied to the ground electrode 11 or the high voltage electrode
12, it is possible to start the electrical discharge stably from an
instant when the pulse voltage is applied.
[0188] When the electrical discharge is started, if high frequency
voltage higher than voltage when the electrical discharge is
started is applied to the ground electrode 11 or the high voltage
electrode 12, it is possible to start the electrical discharge
stably, and it is possible to reduce the applied voltage when the
electrical discharge is started.
[0189] Further, if DC voltage is applied in between the ground
electrode 11 and the high voltage electrode 12 to take place the
electrical discharge, it is possible to always apply constant
voltage in between the ground electrode 11 and the high voltage
electrode 12 and thus, it is possible to stable the electrical
discharge over the entire time. Especially, if negative voltage is
applied to the high voltage electrode 12, it is possible to make
the electrical discharge further stable.
[0190] Further, only a tip end of the high voltage electrode 12 may
be made of platinum. As the high voltage electrode 12, it is
possible to use a metal pipe, a metal rod, a carbon rod, a Ti--Pd
alloy rod and the like, and the high voltage electrode 12 is not
especially limited only if it can generate plasma.
[0191] A water reservoir 80 is formed between an outer periphery of
the reaction pipe 13b and an inner surface of the body case 10 so
as to surround the reaction pipe 13. Water is supplied to the water
reservoir 80 from a water-supply pipe 16B provided in the body case
10. The water supplied to the water reservoir 80 is supplied into
the reaction pipe 13b from an upper end of the water reservoir 80.
Then, the water supplied into the reaction pipe 13b flows downward
along an inner wall of the reaction pipe 13b, and forms a water
layer over the entire surface of the inner wall of the reaction
pipe 13b.
[0192] Since the water layer is formed over the entire surface of
the inner wall of the reaction passage 13, the plasma and water
come into contact over a wide area. Therefore, water vapor
generated by the contact between the plasma and water can be
entangled into plasma efficiently. Thus, the decomposition of the
harmful material is facilitated, and the water-soluble reaction
product can be absorbed in water efficiently. Thus, the decomposing
and separating efficiency of the harmful material can be enhanced.
Further, when the harmful material is solid or liquid, if the
harmful material is supplied from the water-supply pipe 16B to the
water reservoir 80 through the introducing pipe 13a alone or
together with water and the harmful material is allowed to flow
downward to the inner wall of the reaction passage 13 together with
water, it is possible to bring the harmful material and plasma into
contact with each other to decompose the harmful material.
[0193] Further, since the reaction pipe 13b is cooled by water in
the water reservoir 80, it is possible to prevent a temperature of
the wall surface of the reaction passage 13 from excessively
increasing. Therefore, it is possible to prevent all the water
flowing downward on the inner wall of the reaction passage 13 from
being evaporated halfway through the reaction passage 13. Thus,
since the inner wall of the reaction passage 13 is always covered
with the water layer, erosion of the inner wall of the reaction
passage 13 which may be caused by the reactive species can be
prevented.
[0194] Furthermore, since the ground electrode 11 is provided along
the inner surface of the reaction passage 13, water flows along the
inner surface of the ground electrode 11. For this reason, the
ground electrode 11 is automatically cooled, and erosion of the
electrode can be suppressed. Further, since a harmful material
passes inside the water layer formed on the inner surface of the
ground electrode 11, the ground electrode 11 does not act as a
resistance when the harmful material flows through the reaction
passage 13.
[0195] If water to be supplied from the water-supply pipe 16B is
previously heated, water heated by heat of plasma can become water
vapor efficiently and thus, water vapor can be supplied to plasma
efficiently.
[0196] Next, other embodiments of the processing apparatus for
subject A will be explained based on FIGS. 25 to 28. Only structure
peculiar to each embodiment will be explained below.
Embodiment shown in FIG. 25
[0197] In this embodiment, the ground electrode 11 is a rod-like
electrode which is in parallel to a center axis of the reaction
passage 13.
[0198] As shown in FIG. 25, the rod-like ground electrode 11 is
provided on a center axis of the reaction pipe 13b, i.e., on a
center axis of the reaction passage 13.
[0199] Therefore, the ground electrode 11 is not completely covered
with water which flows downward along the inner wall of the
reaction pipe 13b, and a portion of the ground electrode 11 is
exposed from the water layer without fail. Thus, plasma formed
between the ground electrode 11 and the high voltage electrode 12
comes into contact directly with the ground electrode 11 and
therefore, power loss which may be caused by water can be
eliminated.
Embodiment shown in FIG. 26
[0200] In this embodiment, the ground electrode 11 is vertically
movably provided in the reaction pipe 13b.
[0201] As shown in FIG. 26, the ground electrode 11 is vertically
slidably mounted on the inner surface of the reaction pipe 13b. A
supporting rod 11b is mounted to a lower end of the ground
electrode 11. The supporting rod 11b is vertically movably mounted
in a case of the processing apparatus for subject A which is not
drawn along a center axis of the reaction pipe 13b.
[0202] Therefore, if the supporting rod 11b is vertically moved
along inner surfaces of the ground electrode 11 and the reaction
pipe 13b, it is possible to vary a distance between the ground
electrode 11 and the high voltage electrode 12.
[0203] Therefore, if the ground electrode 11 is upwardly moved to
shorten the distance between the ground electrode 11 and the high
voltage electrode 12 when the electrical discharge is started, it
is possible to easily form plasma, and to reduce the voltage when
the electrical discharge is started.
[0204] Further, after the plasma is formed, if the ground electrode
11 is downwardly moved along the reaction pipe 13b, it is possible
to form plasma long along the reaction passage 13 and thus, the
reacting area between the plasma and a harmful material can be
increased. Thus, the decomposing and separating efficiency of the
harmful material can be enhanced.
[0205] When the ground electrode 11 is vertically moved, if voltage
is controlled such that the electrical discharge current is
maintained at a constant value of higher, it is possible to move
the ground electrode 11 in a state in which plasma is held
stabilized.
[0206] Further, a method for vertically swinging the ground
electrode 11 is not limited to the above-described method. It is
possible to employ a method in which a magnetic substance such as
an iron piece is fixed to the ground electrode 11, and the ground
electrode 11 is moved from outside using a magnet. When a
cylindrical reaction pipe 13b is used, it is possible to employ a
method in which a helical groove is formed in the inner wall of the
reaction pipe 13b, a projection which can slidably be engaged with
the groove is provided on the ground electrode 11, the ground
electrode 11 is rotated around its center axis to move the ground
electrode 11 vertically. The method is not especially limited only
if the ground electrode 11 can vertically be moved along the center
axis of the reaction pipe 13b.
Embodiment shown in FIG. 27
[0207] In this embodiment, a plurality of ground electrodes 11 are
provided in the inner wall of the reaction pipe 13b along a center
line of the reaction pipe 13b. As shown in FIG. 27, the plurality
of ground electrodes 11 are independently provided in the inner
wall of the reaction pipe 13b along the center line of the reaction
pipe 13b. The ground electrodes 11 are respectively connected to
the switching circuit 70 through a plurality of electric wires 71.
The switching circuit 70 are a switch and the like using a relay
circuit or a semiconductor. The switching circuit 70 switches over
the electric wires 71 and the ground electrodes 11.
[0208] Therefore, if the ground electrode 11 to be connected to a
ground 72 is switched over, it is possible to increase and reduce a
distance between the high voltage electrode 12 andthe ground
electrode 11 which receives electrical discharge from the high
voltage electrode 12. Thus, if a ground electrode 11 which is close
to the high voltage electrode 12 is energized when the electrical
discharge is started, it is possible to easily form plasma.
[0209] If a ground electrode 11 to be energized is changed to
another ground electrode 11 which is further from the high voltage
electrode 12 in sequence after plasma is formed, a length of the
plasma can be increased. Therefore, since a space where the plasma
and the harmful material are reacted with each other is increased,
the decomposing and separating efficiency of the harmful material
can be enhanced. Further, since the length of the plasma can be
changed only by changing the ground electrode 11 to be energized, a
structure of the apparatus can be simplified.
[0210] The switching circuit 70 is not limited to the
above-described circuit only if the switching circuit 70 can switch
over the connection with the ground electrodes 11.
Embodiment shown in FIG. 28
[0211] In this embodiment, the high voltage electrode 12 is
vertically movably provided. As shown in FIG. 28, the rod-like high
voltage electrode 12 is provided coaxially with a center axis of
the reaction pipe 13b, and the high voltage electrode 12 is mounted
to an upper end of the body case 10 such that the high voltage
electrode 12 can vertically move along the center axis of the
reaction pipe 13b.
[0212] Therefore, when the electrical discharge is started, if the
high voltage electrode 12 is brought close to the reaction passage
13, it is possible to easily form plasma. If the high voltage
electrode 12 is moved away from the reaction passage 13 after the
plasma is formed, a length of the plasma is increased, a space
where the plasma and the harmful material are reacted with each
other is increased and thus, the decomposing and separating
efficiency of the harmful material can be enhanced. Further, when
the harmful material is gas, since it is possible to increase a
reaction amount between the plasma and the harmful material whose
flowing speed before entering the reaction passage 13 is slow, the
decomposing efficiency of the harmful material can be enhanced.
[0213] A method for vertically swinging the high voltage electrode
12 is not limited and any method can be employed only if the high
voltage electrode 12 can be vertically moved along the center axis
of the reaction pipe 13b.
INDUSTRIAL APPLICABILITY
[0214] According to the present invention, even fluorocompound such
as PFC including CF.sub.4 can effectively be decomposed because
such compound is brought into contact with plasma in a narrow space
for sufficient time. Since the structure of the apparatus is small
and simple, the apparatus can be added to each process chamber.
[0215] Further, according to the invention, the exhaust gas is
influenced by plasma while passing through a long distance in a
narrow cross section and thus, the decomposition efficiency of the
exhaust gas becomes high.
[0216] Further, according to the invention, if absorbent is charged
into the plasma chamber on the outlet side of the reaction passage,
the decomposed gas components can be collected.
[0217] Further, according to the invention, if the wool-like
buffering agent is used, it is possible to disperse the powder
absorbent in the plasma chamber substantially uniformly and thus,
the gas can be collected effectively.
[0218] Further, according to the invention, since water or water
vapor is supplied in the vicinity of plasma, a water-soluble
reaction product in the exhaust gas can swiftly be discharged from
vapor phase, and decomposition can be facilitated.
[0219] Further, according to the invention, since the plasma
generated in the reaction passage is allowed to contact water or
water vapor, the reaction time of plasma becomes long, and
decomposition can further be facilitated.
[0220] Further, according to the invention, even if the amount of
flow of the exhaust gas is small, it is possible to fully fill the
reaction passage with plasma.
[0221] Further, according to the invention, since water in the
water reservoir becomes a liquid electrode, plasma is generated
between the high voltage electrode and the water surface, and the
exhaust gas is decomposed while passing through this plasma region.
Among the decomposed components, water-soluble component is
collected in water and thus, the water-soluble component can be
discharged together with water and disposed.
[0222] Further, according to the invention, water which was
evaporated from water surface below the reaction passage made of
insulating material is returned into the water reservoir through an
outside of a substantially truncated conical insulating material.
Therefore, a waterdrop is not attached to the reaction passage, and
disturbance is prevented from being applied to electric
discharge.
[0223] Further, according to the invention, since plasma generated
in the reaction passage is allow to approach and water or water
vapor is supplied, the reaction with water becomes most active, and
decomposition of the exhaust gas can be facilitated.
[0224] Further, according to the invention, since hot water or
water vapor which was heated while passing through the waterway can
be supplied into the reaction passage, reaction between plasma and
water is effectively carried out, and decomposition is
facilitated.
[0225] Further, according to the invention, a harmful material can
be decomposed efficiently, and even if the harmful material is
fluorocompound such as PFC including CF.sub.4, the harmful material
can effectively be decomposed, the apparatus has a small and simple
structure, and the apparatus can be added to each process chamber.
Further, the decomposition of the harmful material is facilitated,
and since a water-soluble reaction product can efficiently be
absorbed in water and thus, the decomposing and separating
efficiency of a harmful material can be enhanced.
[0226] Further, according to the invention, since the reaction
passage inner wall is always covered with the water layer, it is
possible to prevent erosion of the reaction passage inner wall
which may be caused by reactive species.
[0227] Further, according to the invention, the ground electrode is
automatically cooled, and it is possible to suppress the erosion of
the electrode. Further, the ground electrode does not act as a
resistance when the harmful material flows through the reaction
passage.
[0228] Further, according to the invention, since the ground
electrode comes into contact directly with plasma, power loss
caused by water resistance can be eliminated.
[0229] Further, according to the invention, it is possible to
easily form plasma when the electrical discharge is started.
Further, since a space where plasma and a harmful material are
reacted with each other after the plasma is formed can be
increased, the decomposing and separating efficiency of a harmful
material can be enhanced.
[0230] Further, according to the invention, if the ground electrode
which is close to the high voltage electrode is energized when
electrical discharge is started, plasma can be formed easily. After
plasma is formed, if a ground electrode to be energized is changed
to a ground electrode which is away from the high voltage electrode
in sequence, a length of the plasma can be increased. Therefore,
since the space where the plasma and a harmful material are reacted
can be increased, decomposition and separation efficiency of the
harmful material can be enhanced. Further, since the length of
plasma can be changed only by changing an electrode to be
energized, a structure of the apparatus can be simplified.
[0231] Further, according to the invention, it is possible to
easily form plasma when the electrical discharge is started.
Further, since a space where plasma and a harmful material are
reacted with each other after the plasma is formed can be
increased, the decomposing and separating efficiency of a harmful
material can be enhanced. It is also possible to enhance the
decomposing efficiency of the harmful material.
[0232] Further, according to the invention, it is possible to keep
a surface of the high voltage electrode chemically stable, it is
possible to prevent erosion of the electrode which may be caused by
the harmful material.
[0233] Further, according to the invention, a water-soluble
reaction product discharged from the flow-outside of the reaction
passage can efficiently be absorbed by water and removed, and it is
possible to prevent the exhaust side of the apparatus from being
damaged by heat.
[0234] Further, according to the invention, since the exhaust gas
can be decomposed under atmospheric pressure, it is possible to
reduce the processing apparatus for subject in size. Since the
exhaust gas is processed on the flow-out side of the roughing
vacuum pump, water does not reversely flow toward the process
chamber, the plasma system is not damaged and its lifetime is not
shortened. It is easy to add the apparatus to each process
chamber.
[0235] Further, according to the invention, gas which was not
decomposed by a first processing apparatus for subject provided in
the roughing vacuum pump and remained can be decomposed by a second
processing apparatus on the flow-out side of the roughing vacuum
pump. Therefore, it is possible to further enhance the decomposing
efficiency of exhaust gas.
* * * * *